48 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Frenzel is especially important, because it gives a careful account of the 
structural conditions of the genus studied by him, though even he did 
not make use of sections to ascertain the minuter details of structure. 
At the suggestion of Dr. Mark, I began in the autumn of 1895 an 
investigation of this peculiar and interesting parasite of Termes flavipes, 
in the hope of being able, by means of more recent methods, — especially 
sectioning, — to add something to what was already known concerning 
them. An excellent 1.5 mm. homogeneous immersion by Zeiss has been 
of much value to me in studying the minute details of structure. In 
October I captured some of the White Ants, both “workers” and 
“soldiers,” in the woods near Cambridge, and on opening the intestine 
of one of them found it swarming with the same kinds of parasites that 
Leidy had discovered in his New Jersey Termites. 
1. Trichonympha agilis. 
Plate l: Plate 2; Plate 3, Figs. 24-26. 
I have represented in Figures 1 and 2 what seem to me fairly normal 
and characteristic appearances of a quiescent T. agilis, and in Figure 3 a 
view of the head end, seen from the anterior pole. My figures should 
be considered, however, simply as in a measure supplementary to those 
of Leidy. His observations were so careful and accurate that 1 have 
almost no modifications or corrections of his description to suggest; but 
I shall be able to add something to his account. 
Upon seeing one of these peculiar animals, the question immediately 
arises, Wherefore such a remarkable cloak of cilia? Well developed 
locomotor organs are the last thing one would expect to find in a para- 
sito whose food is close at hand and whose field of exploration is so 
limited. With the hope of getting some light on this question, and 
wishing at the same time to discover, if possible, the situation of 
the mouth, I experimented by putting living specimens into various 
fluids; among others, into very much diluted milk. The Tricho- 
nymphe immediately on escaping from the intestine began ploughing 
their way through the milk corpuscles, passing across the field of the 
microscope so rapidly that, in order to follow them, it was necessary to 
keep the slide in constant motion. The various courses traversed by 
them were indicated by paths cleared of the oil globules. Upon watch- 
ing their movements, it presently became apparent that the shortest and 
most anterior cilia were to a very large extent responsible for the mo- 
tion. The longer cilia, those extending backwards to about the region 
